The pressure relief valve is a vital safety component of hot water tanks. If either the temperature or pressure within the hot water heater unexpectedly rises, the valve open and effectively releases the dangerous build-up. If the valve is not working correctly, the tank is at a greater risk of rupture. A leaking pressure relief valve indicates a failure within the valve itself and should be replaced immediately. Not only is a leaking valve faulty, but it will slowly drain water from the hot water tank.
Place a bucket under the drain line attached to the leaky pressure relief valve. This will catch the leaking water and any water that spills out during the removal of the valve.
Shut off the power to the tank. Electric hot water heaters should be turned off at the circuit box. For a gas hot water tank, turn off the gas.
Turn on the hot water faucet at a sink or bathtub. Permit the hot water to run for roughly 15 minutes. This will reduce both the amount and temperature of water in the tank. After the 15 minutes have passed, shut off the hot water faucet.
Turn off the cold water supply valve located near the top of the hot water heater. If you're not sure which line is the cold water supply, look on top of the tank. Most tanks will clearly mark which line supplies the cold water and which line carries hot water from the tank.
Disconnect the drain pipe from the leaking pressure valve. Turn the pipe counterclockwise with a pipe wrench.
Remove the faulty pressure relief valve from the hot water tank. Attach the pipe wrench to the hexagonal nut near the bottom of the valve. Carefully turn the valve counterclockwise. Due to corrosion, the valve may be difficult to remove at first. If necessary, spray a small amount of penetrating oil onto the threads of the valve and let it soak for approximately five to 10 minutes.
Wrap Teflon tape around the threaded portions of the drain pipe and the replacement pressure relief valve. The tape will help seal the new valve, thus preventing future leaks.
Install the replacement pressure relief valve. Turn the valve into the tank using your hands. Ensure that the valve is correctly screwed into the tank, otherwise it will not work correctly. Once the valve is turned as tight as possible with your hands, use the pipe wrench to finish turning the valve tight. Connect the drain pipe to the replacement valve.
Turn on the cold water supply valve near the top of the tank. Turn on a hot water faucet at a sink or bathtub. This will remove air trapped in the hot water tank or hot water lines. Allow the faucet to remain open until it releases a steady flow of water, uninterrupted by air.
Turn on the electricity or gas to the hot water tank. If it was properly installed, the replacement pressure relief valve should not leak.